Nokia NPD-4 Series Troubleshooting - Gps page 11

CCS Technical Documentation
GPS Self-Test
The GPS Quick Test function from Phoenix performs an internal Self-Test that allows the
GPS BB ASIC to check for internal faults.
Code Download
The code store inside the GPS BB ASIC is volatile. As a result, each time power is applied
to the ASIC, the code that runs there must be re-downloaded from the CE. If this process
does not complete correctly, the GE will not work. The interface protocol utilized for this
process is the Universal Synch/Asynch Receiver Transmitter (USART), and the pins on the
GPS BB ASIC are labeled U1Tx, U1Rx, U1_DATA_RDY, and U1_CLK. To determine if this
interface is active, check for activity on these lines at power up. Each of these lines
should have a short burst of activity immediately after power is applied. To capture these
signals, you will need to set the storage scope to single sweep or triggered mode (see
Figure 5).
SPI Interface
The SPI interface is a three-line synchronous serial interface used by the GPS BB to com-
municate to the GPS RF. These lines are called SPI_CLK, SPI_DATA, and SPI_EN. Activity
should be seen for a short period on these signals each time a mode switch is made (e.g.,
between ON and OFF mode in the "GPS Receiver Control" tab of the GPS component in
Phoenix). See Figure 6.
Issue 1 02/2003
Figure 5: GPS Code Download U1 CLK U1 RX
Nokia Corporation
Troubleshooting — GPS
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NPD-4
Page 11